Linear Motion

• Relative- Regarded in relation to something else. Depends on the point of view, or frame of reference.
• Rate- Quantity divided by time.
• Speed- A measure of how fast something is moving.
• Instantaneous Speed- The speed at any instant.
• Velocity- The speed in any given direction.
• Acceleration- The rate at which the velocity is changing.
• Free Fall- Motion under the influence of the gravitational force only.
• Elapsed Time- The time that has elapsed, or passed, since the beginning of the fall.
• Average Speed- Path distance divided by time interval.

Examples

2.1 - Motion Is Relative

• Everything moves relative to the sun and the stars
• Even when something is at rest, it is moving relative to the sun, stars, or galaxy
• All motion is relative to something else

• The speed of an object measures how fast the object is moving
• Speed is the rate at which something is moving (rate = divided by time)
• To describe speed, units are combined (mi/h, km/h, etc.)
• Instantaneous speed describes the speed of an object at any instant
• Average speed is the total distance covered divided by the time

• Velocity is the speed of an object in any given direction
• Speed and velocity are very similar, but velocity deals with direction and speed does not
• Constant velocity requires constant speed and direction
• If the speed or the direction of an object changes, the velocity changes

• The rate at which the velocity changes is acceleration
• A car accelerates when the driver steps on the gas pedal, which makes the car move faster
• If something has a good acceleration, it does not mean that it is fast, but that it can change its velocity quickly
• Acceleration is a change in speed and direction

• If an object is in free fall, there is no air resistance on the object and gravity is the only force acting on it
• The elapsed time of the fall is the time from the beginning to the end of the fall
• The acceleration of an object falling freely is about 10 meters per second squared

2.6 - Free Fall: How Far

• Speed and distance are not the same.
  

2.7 - Graphs of Motion

• You can use graphs to visually describe relationships between velocity and acceleration
• Linearity- When the graph shows a straight line
• Slope- Vertical change divided by the horizontal change for any part of the line
• Parabolic- When we double one variable, the other is quadrupled

2.8 - Air Resistance and Falling Objects